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Chemical Injectors - Learn how they work!
Chemical injectors add soap to your pressure washer's water flow. There are different styles of injectors, but most after-market injectors are "downstream" injectors - which means that the soap is injected after the pump. The other style is called "upstream", where the cleaner is injected ahead of the pump. Upstream injectors are high pressure applicators, while downstream injectors are low pressure applicators.
In a downstream injector, the venturi action caused by water passing through the injector over an open tube is how the soap is sucked into the flow. A ball and spring arrangement acts as a valve (which opens under low pressure to allow suction). The cleaner then travels through your hose, gun, and wand.
Downstream injectors are "low pressure" injectors, which means that the pressure has to drop below a certain level before the injector starts to draw. That is the purpose of your black "soaper" nozzle, which has a large orifice and drops the pressure in the system. A downstream injector will never work with your standard high-pressure nozzles.
Standard fixed injectors are 10:1 injectors, which means they draw 1 gallon of soap for every 10 gallons of water that pass through them. "High flow" injectors generally are 4:1 ratio, which means 1 gallon of cleaner is pulled in for every 4 gallons of water flowing through the pressure washer. Adjustable or variable injectors have a range of draw (usually between 4:1 and 10:1) but don't often have markings to tell you what they are set at. An adjustable injector gives you the freedom to play around with your soap mix. Sometimes injectors are identified by percentage, which is easy to interpret. A 20% injector is a 4:1 injector.
Injectors also are sized to fit your power washer. Common injector sizes include the 2-3 GPM range, the 3-5 GPM range, and the 5-8 GPM range. If your pressure washer is rated at 3 GPM, you have to choose between the 2-3 GPM or 3-5 GPM size. Often going with the small size is the best choice - but not always. We cannot tell you which one is right for your machine, so we recommend that you take a good look at your old injector. The size is usually stamped somewhere on that old injector.
Some injectors are rated as "chemical" or "acid". Generally speaking, an acid injector will work with any cleaner (acid or alkaline) but acids will ruin a "chemical" injector.
Frequently you are better off buying an Injector Kit, which includes a new hose and strainer. The couple of dollars extra is worth the money, as problems with old hoses include air leaks that can end up causing failure in your new injector.
One last point: if you are installing a replacement injector, pay close attention for little arrows on the body of your new injector. They indicate the direction of water flow. The arrow always points AWAY from the pump towards the hose.
Unloaders - Learn how they work!
Unloaders are usually a brass part with a black knob or an adjusting nut that is connected on the high-pressure side of your pressure washer pump.
Unloaders are a safety system for your pump. Unloaders are spring valves that open under adverse pressure build-up in the pump, allowing a little cool water (contained in that short hose) to enter the pump while allowing some of the overheated water to leave.
This high pressure and high heat occurs when we allow a pump to run during a time when the trigger is not being pulled. Every time the unloader functions, a little of the life of that spring is used up.
Most manufacturers tout the unloader as an adjustable pressure regulator because turning the knob and relieving pressure on the spring will lower your pressure output. The problem with that train of thought is that adjusting the knob causes the unloader to open and close at a lower pressure - so it "cycles" more often and wears out faster. If you never adjust the unloader and don't let your pressure washer idle without pulling the trigger every minute or so, chances are your unloader will never wear out. On the other hand, if you often dial down the pressure with the unloader knob or frequently allow your power washer to idle without relieving the pressure by pulling the trigger, chances are you will be replacing that unloader every year or two.
Depending on the design of the unloader valve, it will sense either the build-up of pressure or the lack of water flow. When the valve opens, the water is allowed to move to the low-pressure side of the pump. The valve stays open until you pull the trigger which releases the pressure or restarts the flow. With the valve is open (when it is in by-pass mode) the water simply recirculates from the high-pressure side (outlet) to the low-pressure side (inlet). This is a short-term fix for a problem, and the unloader will only protect the equipment for a reasonably short period of time. Left to idle with the trigger gun closed, the water inside your pump keeps getting hotter and hotter.
Enough damage to the pump occurs in just a few minutes of letting your pressure washer idle with the trigger gun closed to put a big dent in your paycheck. Three minutes of idling is enough to cause extensive damage to seals and packings. Five minutes can even cost you the pump itself.
The thermal shock of allowing cold water into a pump that has become super-heated this way will often crack the ceramic pistons and generally damage the wet end of your pump, and replacement parts and labor can be as expensive as buying a whole new pump.
We are often asked to suggest the "right" unloader for a contractor’s machine. This is one of those personal preference questions, and I hate to suggest one brand or type over another. We prefer that the customer select the type and brand of unloader he wants to work with. Here is some information to help you make an informed decision.
Pressure-type (or "trapped pressure") unloaders sense the pressure in the system and open when pressures hit a certain point. It is called a trapped pressure unloader because the pressure is trapped throughout the system. The hose and trigger gun are still under full pressure even when the unloader valve opens. When you pull the trigger, there is an instant burst of highly-pressurized water ready to go. Operators feel a lot of shotgun-style kick-back when the trigger is pulled on one of these systems. Trapped pressure unloaders are by far the most common found, and a typical example is the YU-2140 by General Pump (a.k.a. the "green spring" unloader).
A variation on the trapped pressure design is the compensating type unloader. This is essentially a trapped pressure unloader with a compensating design that limits the burst of pressure when the trigger gun is opened. Typically, a compensating unloader limits pressure in the system to between 10% and 25% of full pressure. One of the most popular compensating unloaders is the VB10 by PA, which is rated at 3600 PSI but drops the pressure in the system to around 400 PSI when in bypass.
Flow unloaders sense a lack of water flow and respond by opening the unloader valve. In this style of unloader, no pressure is trapped in the system with the trigger gun closed. There is no big burst when the trigger gun is opened, either. Pressure usually comes back slowly over several seconds. The most common flow unloader seen today is the K-7 by General Pump.
UMR (Unloader Made Ready) Kits make unloader replacement easy and fast. They come with an inlet filter, a quick-connect outlet, push-on hose barbs (no hose clamp needed), teflon tape, and an instruction sheet. The difference in cost is around $15 more over buying the unloader alone, and is well worth the price for the convenience.
